Spark plug



May 29, 1.928. w. L. PHILLIPS SPARK PLUG Filed March' 1, 1922 PatentedMay 29, 1928.

WILLIAM L. PHILLIPS, OF BROCKTON, MASSACHUSETTS.

SPARK PLUG.

Application ined Maren 1, 1922. j serial No. 540,317.

This invention relates to improvements in sparkplugs. More especially itrelates to sparkplugs of the type comprising an auxiliary or subsidiarygap in the ignition circuit. The main purpose of all spark plugs is thetransmission of a current to'` a place Where it can be caused to ignitea charge of explosive gases Within an engine adapted to utilize thepower developed by such explosion. To this end, the spark plugs now inuse have supplied the means whereby the current from a magneto or coilis conducted along an insulated electrode into the chamber of thecylinder, there caused to jump a gap to the wall of the plug from whichlthe current may pass olf, usually into the engine walls which actas aground circuit back to the source of potential. The important functionof the spark plug isto conduct the current so that it will positivelyjump the gap, and not become short circuited in any manner before doingso. To insure this result the incoming electrode is usually encased in asubstantial insulator, for practically its entire length. This insulatoror core is usually made large and heavy in order to withstand both thepressure of the electrode, due to the latters expansion when heated, andthe severe strains imposed `by Vcompression 1n assembling the parts ofthe plug; and as a result, the'core occupies nearly all the space withinthe plug, almost to the end of the electrode. It thus furnishes aconvenient surface for the deposition of solid products been found underthese conditions, that if the energy of the current is increased at theinstant the spark would ordinarily jump, that it actually will jump thegap in'spite of the fouling. effect already described. As a means forincreasing the energy available for ignition to overcome the -foulingeffect,"a second or subsidiary ga has been interposed between theprincipe gap and the source of energy, with some satisfactory results;but, so far as I am aware, this subsidiarygap has never been utilized toits greatest capacity. It is usually found in one of three places;integral with the plug; at the Cplug, but not integral with it; orremove from the plug at a point Within or near the distributor. Theiirst of these 10- cations is undoubtedly the most desirable from theviewpoint of electrical efficiency, inasmuch as its action with wrespectto the principal gap is so near the latter that the evil of dissipationis reduced to its minimum. But when placed integral with the plug it`has been the practice to leave the subsidiary gap either open to theair, or inclosed in an air-tight container; and its purpose and effecthave been to overcome the short-circuiting effect ofdeposit and thusenable a spark to jump the p`rincipal"`gap. The action of the subsidiarygap, however, has in no way been utilized either to prevent the creationof such depositorto break it up and eliminate it after its formation hasbegun. `In contrast with this merc effort to surmount the evilconditions due to` fouling and to operate more orless effectively inspite of them, it is an important purpose of the present invention toget' rid of or to prevent the fouling. y

It is amongthe objects of the invention to so construct a spark plugthat both the principaland subsidiaryl gaps are Within the explosive"mixture, whereby the spark across each gap may be utilized to fire thecharge, thus at east doubling the igniting effectiveness of the plug.Other objects ofthe invention are, to intensify the principal spark` bythe use of the subsidiary gap-in the circuit; to augment theintensifying eii'ect of the subsidiary gap by placing it in a. mediumwhich is under compression and thus of increased density correspondingto a greater break-down voltage; to provide means by which thesubsidiary gap may be adjusted both when the engine is idle and whilerunning; to utilize t-he explosion caused by the auxiliary spark toclean an internal electrode and prevent deposit thereon of carbon or oiland, if desired, to clean an electrode directly connected with 4theoutside conductor; to provide means permitting the auxiliary spark andits resultant explosion to be visible, thus signalling the lili llf)

actual firing of the explosive charge; to provide an insulated supportfor the internal electrode which shall be easily molded, light andself-cooling; to so position this insulator within the plug that it willbe subjected to substantially equal degrees of heat and pressure on itsopposite surfaces; and to so arrange and dispose the several parts ofthe plug as to provide a closed passage through the plug which may beopened when desired to permit priming of the plug, the testing of thecompression, or the utili-y zation of the latter for tire inflation orother purposes.

These various objects are attained by supporting within a hollow of aspark plug a separate insulated internal electrode to which the currentmay jump from the external electrode across the subsidiary gap and fromwhich it may jump across the principal gap, the said hollow constitutinga part of the explosive chamber of the engine in which both gaps arefilled by the gaseous mixture under compression. The support for thisisolated electrode is provided with a passage through which the gasesare foi'ced during the compression and expansion strokes of the piston,the passage being so arranged as to cause the moving gases to act as acleaning agent on the internal electrode, the inner portion of theexternal electrode and on the support itself, thereby preventiner anyundue deposit of the products of comiustion and eliminating any foulingor short circuiting of the plug. The walls of the plug surrounding theregion in which the subsidiary gap is located may be madenon-transparent,

or transparent or provided with windows, through which the igniting ofthe charge may be seen. The terminal of the plug to which the outsideconductor is attached comprises elamping means for holding an upper orexternal electrode in adjustable relation to the internal electrode, andis so arranged that it may be withdrawn slightly n the plug to open arestricted passage thercthrough from the cylinder chamber to theatmosphere, or may vbe wholly removed to allow a compression gauge orair pump to be attached. In the embodiments shown in the accompanyingdrawings, various applications of the invention ai'e shown, but it is toe understood that these adaptations are merely illustrative. It isintended that the patent shall cover by suitable expression in theappended claims whatever features of patontable novelty exist in theinvention disclosed.

Referring to the drawings:

Figure 1 is an elevation in medial section showing one form of plugembodying the invention Figure 2 is a plan in section on line 2-2 ofFigure 1;

Figure 3 an elevation, partly eut away to a medial section, showing amodification;

Figure 4 is a horizontal section on line 4 4 of Figure 3;

Figure 5 is an elevation of a detail of another modi tication;

Figure (i is an elevation in medial section of a plug showing othermodifications in the design and arrangement of the parts;

Figure 7 is a plan of Figure 6 in section on line (3f-6;

Figure 8 is an elevation in section showing a modified foriii of theplug terminal; and

Figure 9 is an axial section of a further modification of the invention.

In the drawings, a spark )lug base 10, threaded exteriorly at one en(for engagement with an engine casing (not shown) is bored throu hout its,length to permit an internal con( uctor or electrode 12, to besnpported axially therein by a tubular insulating element 14,hereinafter called a core, having a flange head and holding portionseating on the upper edge of tliebase, and a thin walled tubular bodyportion 16 projecting within the base to form an insulating sleeve aboutthe electrode for a considerable portion of its length. This internalconductor is secured to its support by clamping nuts 18, one of whichpresses insulating element, and the other of which rests against theunder surface of the same, in the dee recess 22 within the bod portion16, which ias the aspect of an annu ar chamber about the electrode 12.The lower end of the latter is near a sparking terminal 24, extendingradially inward from the wall of the base being separated therefrom by agapy a hollow, iion-ctuiducting cap or cover 32` held tightly inregister with the insulated core 14 by a collar 34 threaded on the upperexterior surface of the base 10. This collar is flanged inward at itstop to engage anr external flange around the bottom of the cap, so thatupon the collar being turned on its threads it will clam the cap 32, theinsulated su port 14, an the base firmly together, t ere being suitablegaskets or washers between the abutting surfaces to make the jointsleak-proof under the working pres- Sures in' the cylinder, `The chamber35 ofV j on the topl surface of the head of the said iolding and the cap32, is connected with the annular chamber 22 by a series of holes 36through the head ot' the insulating core, constituting Y passages torthe admission of gas :from the engine cylinder to the chamber in the topol` the plug, and for its'expulsion. s

`The upper or external electrode 30 is held in axial alignment Withinasleeve 258 which passes through'the top ot' the cap and is securelyclamped thereto by a nut 4l) threaded exteriorly on the sleeve, thethreaded portion ot' the latter extending upward to form a stem for asupporting nut l2 Whose body portion engages the. stein, and throughwhich the electrode pro-jects and to which it is locked by the lockingnut le on the protruding end ol" the electrode. through the sleeve 38 islarger in `cross section than the electrode 30, so that the latter issurrounded by a small annular` `space Which opens into the chamber atYone end, and at the other is closed by the tight lit of the stem inthesupporting nut when the latter isscrewed down to its limit on the sleeve38. This space, however, may be vented to the atmosphere, upon thesupporting nut being unscreweda short distance,`

there being radial holestG through the body of thenut close to its headwhich Will connect with the space left above the end of the sleeve 38when the nut is backed a..

thread or two. It it is desired to prime the cylinder, the supportingnut, and with it the upper electrode, may be entirely removed from thesleeve 3S. The liquid gasoline, ether or other priming substance maythen be poured into the top ol. the plug, whence it will pass throughthe chamber 35, passages 36, chamber and the bore of the plug into theengine cylinder. This mode of priming is very useful in that the liquidin passing through the plug dampens surfaces in the immediate vicinityof the' gaps whereby upon occurrence of the sparks across the gaps anexplosion vvill of certainty occur. The removal ot' the supporting nutand electrode also enables a gaugeto be attached to thestem for testingjthecompression o-tthe cylinder; or if a pump is at-` s tached, insteadot a gauge, the pressure of the cylinder `may be utilized to operate thepump for blowing up tires `or doing otherl useful Work.

The terminal ol"` the outside conductorv :from the source' of electricSenergy may be slipped around a neck portion of the locking nut 44, ormay be clamped between-this nut and a binding nut 48 screwed thereon, or

may be clipped over the top end oftheV binding nut its lf. i s Whentheplug has been 'placed in the en-` gine ycylinder head,` and thecompression stroke takes 'place the explosivemixtureis forced into thebore of the spark plug base and thence through the passages 36 intothedirected` to this particular plu The holev able `timing device anddistributor the elecs trofnurtive force of the ignitionsystem `at afavorable time tor the igniting orthe charge.' Art the innerterminusoftheex-` `another slnirlrjuinps Vthe principal gap between thc terminalof the internal. electrode l2 and the terminal The. action isso rapidthat the sparks are almost si1nultanons; and even though the gases inthe upper chamber are actually ignited first the second spark occursbefore the burning has beentransmitted to the gases about the sec ond`gap, so thatthe latter spark also sets lire to the explosive mixture.Thus two sep arateigniting sparks are provided by one circuit throughthe plug, one of which, the principal, is intensitied'by the other. Thisis particularly so in a plug embodying the present invention becauseofthe fact that' the auxiliar gap is through a mixture ot', gases undercompression ofthe cylinder.` As the density ot a gas is directlyproportional to itsl pressure, and its resistance is directly.proportional to its density, it fol lows that theenergy required toovercome the resistauceiof a gap thus under compression is substantiallylarger thanit'the gap` were iu freev air or merely ineased in anairtight chamber. When'the increased energy required to overcome theresistance of the subsidiarygap is built up and the current leapsVacross this gap, p aeticallyall `of this energy is then available forintensifying the spark across the principal rap, and as a result theprincipal spark is ighly energized and its el'ectiveness'increased forignition of `the engine charge. i

The expansion ot' the burning gases in the chamber 35 causes them topass down rapid` lyl througlfi the passageways 36 into the chamber 22andthence along past the eleotrode A12 into the engine cylinder` This 76tei-nal electrode it buildsvup,r momentarily,

HIJ

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high `speed of flow ol the gas through the -it may easily be removed byunscrewing the nut 42 until the radial holes lr6` vent the space `to theatmosphere. The degree of y lo longitudinal movement of this nut is soslight that even though the gap 28 be increased by the unscrewing of thenut 42 and the consequent movement of the upper electrode, the sparkwill continue to jump and the explosion to occur; and the pres-` sureresulting from the explosion in the chamber 35 will force any solidmatter in the space about the electrode out through the holes 46.

In order that the operator may see that the plug is properlyfunctioning, transparent means is provided in the top of the plugthrough which the sparking across the subsidiary gap and the flash ofthe resulting explosion are visible. The cap or cover 32 shown in Figure1 Inay be made of any suitable transparent material such as glassespecially made to withstand heat and pressure changes. In Figure 3,`amodified form of a top is illustrated in which a cylindrical transparent'shell 50 is interposed between the support 14 of the lower electrodeand an insulated support 52 of the upper electrode,

the' aligning collar 34 being perforated as at 54 to provide peep holesto the chamber 35. In Figures 6 and 9 a still different method is shownwhereby a glass window 56 Visheld against an annular seat in a sleeve 58by-means of the explosion chamber 35 and windows 54 thereof in that thenature of the combustion in the cylinder can be ascertained by the colorof the flame seen in the chamber of the plug. It has been found inpractice that the color o-f this flame varies in accordance with thekind of explosion taking place in the cylinder. If a very rich mixtureis used the flame will be of one color; if a thin or poor mixture isemployed the flame will be of a different color; and if kerosene orother substances are added to the gasoline, this also causes changes inthe flame color. Accordingly, by a series of experiments a color chartmay be developed, based upon the flame colors oli-different explosivemixtures which will show the relative efficiency of various fuels; andthereafter a comlmrison of the colors of the flamesl produced in theplug with the listings on the chart, will enable the user of the plug toknow the conditions existing in the cylinder at the time the explosiontherein takes place.

A further modification is illustrated in Figures 3 and 4, wherein thelower electrode 12" is made in the form of a hollow stem or tube'fitting tightly within the central bore o f the insulating element 14.The upper end of this electrode is preferably substantially flush withthe top surface of the core, while its lower extremity extends below thecore close to the sparking terminal 24. The opening through this tubeconstitutes the transfer passage for unfred gases from the enginecylinder to the u per chamber of the plug, and for the burmn gases' fromthe upper chamber back to t e cylinder. In consequence of the lattertransfer and because of its proximity to; the lower spark gap, theprotruding end of the tube becomes hotand serves to heat the unburnedgases as they pass upward through it into the chamber 35, thus' aidingtheir ignition, and by so doing, permitting poorer grades of fuel to beused than has heretofore been possible because of inability to fire themunder normal temperatures cxistino' in the cylinder. In a plug equippedwith this particular type of lower electrode the passa e to the upperchamber may be restricted y moving the upper electrode 301V toward thehollow conductor 12"' thus reducing the effective opening of the latterand at the same time varying the sparkA gap. By this means, the amountof gas entering the upper chamber can be regulated to any desired amountand may in fact be entirely cut off by screwing down the upper electrode30 until its conical end seats tightly on the rim of the tubularconductor. This, of course,

will also do away with the auxiliary spark gap and would not be the mostdesired manner of using the plug, but such setting could be adoptedadvantageously in case the transparent cylinder 50 should becomeaccidentally shattered and could not be conveniently replaced at thetime of such accident. By thus closing the passage to the upper chamberthe plug could then function as the ordinary single gap spark plug.

In they type of plug shown in Figure 1, and in the various modificationshereinafter described, the upper spark gap may be closed by bringing theadjacent ends of the electrodes together and making them electricallyintegral. This would make the upper chamber a mere flash chamber inwhichthe gases would be fired b the single spark occurring within the cyliner but even when thus'used, the plug would serve, as lalready described,to indicate by the color of the flame the nature of thee'xplosion'qecurring in the cylinders.

In Figure 5 a modification of the support for the internal electrode isshown in which the sleeve portion y16 isreduced in diameter and setclose to the electrode, and the passages 36 are provided. through theflange portion communicating with the lower chamber on the outside ofthe sleeve 16. In Figure a still different form of support 16 is shown,in which the support has an axial passage throughout its length, in themidst of which the electrode is supported by a perforated disk member 64set into the walls ofthe insulator, through the perfrasures, nor arethey under high'temperaturel at one end and relatively lowtenipcratureat the other. TheV cores are heldin place `by direct clamping pressuresonopposite sides of their flanged portions; `and the pressure on thenuts or othermeanswhich sup-` port the electrode in place are equal andopposite in elfect. Since the explosion occurs above and below andaround the core at practically the same instant, the pressure changesupon and the temperature changes ofthe insulator are substantiallyuniform.`

lVhen the cylinderis being charged the movement of the fresh gasesthrough the plug and passageways vof the `support into the upperchamber, tend to uniformly cool the porcelain and prevent its everbecoming overlieated though entirely located within the explodingchamber. 1 e

` In Figure 6 the upper or external electrode 30 is shown arranged atthe side "of the plug casing instead `ofat the top. Figure 9 alsoembodies this arrangement but shows a further modification of theinvention wherein the internal electrode 12 is supported at the top ofthe plug sothat it projects longitudinally through the bore which issubstantiallyunobstructed by any supporting means, except where tightlyclosed at its upper end. The current is brought into the plug fromtheside through the external electrodeBO, or ifaduplex system of `ignitionis used, another electrode 30 may conduct the second current `to theinternal electrode; "If it were desired to use a system wherein, theignition circuit was to be entirely insulated from the engine. and

not use the "latter as a ground, the forni of plug shown in Figure 9would `lend itself most conveniently'to such an arrangement, in thattlie internal electrode 12` could be entirely removed, the currentconducted through the plug by the external electrodes 30 and 30, thespark occurring across the gap between their ends located'in the bore ofthe plug.`

Figure 8 shows a modification of `the upperelectrode and its`connections, wherein the electrode extends upward so that its externalendmay be engaged by a screwdriver or other tool and the electrode movedforadjustment while the engine is running. The external conductor wouldbe attached to the lock nut 44 or between this nut and the binding nut48. both of Whichwould be removed on the electrode away from thesupporting nut 46, so that the electrode could be withdrawn or inserteduntil the proper e spark gap.

gap was ascertained `under running conditions, after which the lock nutcould be seated against the supporting nut to fix the electrode in theadjusted position, and then the binding nut turned down to clamp theconductor. e e

Although referred ltoas being in a` vertical position, it is evidentthatthe plug of the invention may beset otherwise, at pleasure.` If forany reason the current` is momentarily cut olf from a spark plug of typehitherto known, and the engine allowed to run awhile Iwithout a sparkoccurring, such a plug may become foul by having its gap filled withlubricating oil that has leaked by the piston rings, and itis usuallynecessar to remove and clean the plug before it willI again properlyfunction. But with a plug of the type herein described the upper gap,beingprotected from such oil leakage would tire the charge as soon asthe circuit was restored.` Upon the first firing, the lower gap would becleaned and the normal double-fire condition restored.

I claim as my invention: e

l. A spark plug for the cylinder of an internal combustion engine,having spark gap electrodes in combination with a chamber into whichexplosive mixture of the engine cylinder may be .x forced past saidelectrodes; and other spark gap electrodes within said chamber, inseries with the tirstmen- .l gine cylinder may be forced past saidelectrodes; and other spark gap electrodes Within said' chamber, inseries with the first mentioned electrodes, the spark of which `isadapted to ignite said mixture within said chamber, there being apartition separating the spaces where the two gaps are, support- `ingthe conductor which runs between the gaps, and having an opening forpassage of gases` to and from the second mentioned e forced` to be`ignited by the ino 4. A spark plug for the cylinder of an internalcombustion engine having con` ductors arranged to form two spark gaps inseries, both being set in space accessible to mixture of the enginecylinder, and one of them being between the other and the enginecylinder, whereby the ignition of mixture by that which iS more remotefrom the cylinder causes a rush of gases past the other into thecylinder.

5. A spark plug for the cylinder of an internal combustion engine havingconductors arranged to form two spark ga s in series, both being set inspace accessib e to mixture of the engine cylinder, and one of thembeing between the other and the engine cylinder, whereby the ignition ofmixture by that which is more remote from the cylinder causes a rush ofgases past the other into the cylinder, there being a partition arrangedbetween the 'spaces wherein the two gaps are located, penetrated by apas sage for transfer of the gases from one space to the other.

6. A spark plug, adapted to have one end inserted in the wall of thecylinder of an internal combustion engine, `having spark gap electrodes;and a chamber, within the plug, outside of the engine cylinder, havingcommunication with the engine Vcylinder through one of said electrodesfor passage of gases; said chamber containing said spark gap electrodes.

7. A spark plug for the cylinder of an internal combustion engine havinga plurality ot chambers accessible to explosive mixture from the enginecylinder, and havingspark gap electrodes in each chamber whose sparkignites the explosive mixture therein.

8. A spark plug for the cylinder of an internal combustion engine havingconductors arranged to form two spark gaps in series lengthwise of theplug, both gaps being set in spaces accessible to mixture of the enginecylinder; one of said spaces being outside of the engine cylinder.

9. A spark plug for the cylinder ofv an internal combustion enginehavinv conductors arranged to form two spark gaps in series, both beingset in space accessible to mixture of the engine cylinder and one of theconductors which constitutes a spark electrode being mounted movably inthe plug, toward and from the other electrode of the same gap; andexternal means to move and to fasten said movable conductor.

10. A spark plug for the cylinder of an internal combustion enginehaving a plurality of intercommunicatin chambers in the same plug, eachaccessib e to explosive mixture from the engine c linder; and spark gapelectrodes arrange for ignition of the mixture in each of said chambers.

11. A spark plug for the cylinder of an internal combustion engine,having spark gap electrodes arranged to cause ignition of `the explosivemixture in the cylinder, combined with means comprising a chamber insaid plug connectlng with sald cylinder' and with the outside of saidplug, and a closure for said outside connection adapted to be 65 openedto vent said chamber. o

12. A spark plug for the cylinder of an internal combustion engine,4aving spark gap electrodes arranged to cause ignition of the explosivemixture in the cylinder, combined with a chamber in said plug, a passageconnecting said chamber with the en eine cylinder wherein gases may passto and rom said chamber, and ymeans for regulating the flow of gasesthrough said passage. y

13. A spark plug for the cylinder of im internal combustion engine comrising conductors arranged to form multiple s .ark gaps, a chamber inthe ug removed rom the cylinder and havln communication therewiththrough the hpliw of one of said conductors, whereby gases ma pass toand from the cylinder to the `cham er; a gap in` said chamber betweenthe end of the hollow conductor andk another conductor; the said otherconductor being adjustable whereby the gap and the openin of the hollow.conductor into fthe cham er may be varied simultaneously.

Y 14. A spark plug for the cylinder of an internal combustion e v ine,comprising conductors arranged to orm multiple `spark gaps; a chamber insaid plug removed from the cylinder and havi communication therewiththrough the h ow of one of said conductors whereby gases may pass to andfrom the cylinder i a ga A arranged in said chamber, across which thpecurrent jumps to .ignite the gases therein, thereby causirg4 a pow rushof burning gases through the ho conductor to the cylinder; the saidburning gases heating said hollow conductor which in turn gives up heatto the unburned gases forced therethrough to the chamber.

15. A. yspark plug for the cylinder of an internal combustion engine,having an internal chamber; spark gap electrodes arranged.

to vform a sparkgap therein; a. passage connecting said chamber with theengine cylinder for transfer of gases from one to the other; one of saidelectrodes being arranged in said passage whereby it is cleaned by thegases passing to and from said chamber.

16. A spark plug for the cylinder of an internal combustion engine,having an internal chamber; spark gap electrodes arranged to form aspark gap therein; a passage connecting said chamber with the enginecylinder for transfer of gases fromv one to the other; another passageconnectin said chamber with the atmosphere; an means for regulating theopening of the last mentioned passage.

17. A spark plu having a hollow body portion adapted `to be inserted inthe wall of an internal combustion engine; insulating mcmberssecured tosaid bodyportion, forming a chamber; spark gap electrodes sup# ported bysaid members providing a spark gap in said chamber; and a passagethrough one of said members connecting said cham-V ber with theenginecylinder for transferV of gases from one to the other. i

18. A spark plug having a hollow body portion adapted to bel inserted inthe wall of an internal combustion engine; insulating members secured tosaid body portion forming a chamber; spark `gap electrodes supportedbysaid members providing a spark gap in said chamber; a passage throughone of said members connecting said chamber with the engine cylinder fortransfer `of gases from one to the other, and a passage through anotheror said members communicating with the atmosphere; the said passages andchamber alfording an outlet for the gases; and means externally on saidplug for closing said outlet. i g

19. A spark plug, adapted to have one end inserted iii the ivall of thecylinder of an internal combustion engine, having spark gap electrodes;and achainber, within the plug, outside of the engine cylinder, havingcommunication with the engine cylinder; one of said electrodes beinghollow and having side openings through which the gases are jettedagainst an internall Wall of the plug to clean it. i

2l). A spark plug for an internal combustion` engine having hollowinsulating members whose hollows constitute a passagel between theengine cylinder and the atmosphere; a sleeve through one of saidmembers; an electrode inovably supported on said sleeve and adaptedto bemoved to 'close said passage; and another electrode in the plugforn'iing lwith said movable electrode a sliiark gap. i

21. A' spark plug, adapted to have one end inserted in the Wall of` thecylinder of an internal combustion engine, having spark gap` electrodesin combination with a chamber, within the plug, outside of the enginecylinder, and having' connection with the engine cylinder; one of saidelectrodes having a 'passage through it for transfer of Huid to saidchamber.

2Q. A spark plug having a bo'dy portion inder of an internal combustionengine; a

chamber in said plug beyond said body portion and outside of saidcylinder; electrodes forming a spark gap vin said chamber for `ignitionof gases therein; and a passage through said body portion connectingsaid chamber with the cylinder for transfer of gases from one to theother; said passage having awall adapted toabsorb heat from the hotgases passing from the chamber to the cylinder, and to give up heat tothe cooler gases passing trom the cylinder` to the chamber. i i

` .2A/L1A sparkplug for the cylinder of an internal combustion engine,having a chamber therein outside of the engiiie cylinder; electrodesforming a spark gap in said chamber for ignition of gases therein; and arelatively 'long passage through said plug connecting said chamber withsaid cylinder for .transfer of` explosive mixture to said chamber andfor transfer of burning gases from said chamber tothe cylinder;the Wallsof said passage being of such length as to permit transfer of heatthereto during passage of the burning gases and to permit transfer ofheat therefrom during passage of the explosive n'iixture. y u

v25. A spark plug, adapted to have one end inserted in the wall of thecylinder of an internal combustion engine, having spark gap electrodesin combination with a chamber, within the plug', having connectionwiththe engine cylinder; one of said electrodes being hollow to permitentrance therein of hot gases wherebyI the electrode is heated andcleaned.

26. A spark plug, adapted .to have one end inserted in the Wall of thecylinder. of an intei-nal combustion engine, having spark gapelectrodes; and a chamber, within the plug, having communication withthe engine cylinder; one of said electrodes being hollow and having anopening into said chamber ivheieby gases may pass through the electrodeto and from said chamber.

` 2T. T he combination with an internal coinbustion engine, of a sparkplug extending through a Wall `and into the combustion space thereof,said plug being provided with spark gaps positioned one on each side ofsaid Wall and further provided with a chamber adjacent the outer gap, arestricted opening leading from .said chamber and into the'coinbustionspace ot said engine adjacent the inner gap, whereby the gases explodingin the outer Vchamber are forced through said opening with high velocityand caused to contact the electrodes of the inner gap and purge thesaine, substantially as described.

The combination with an internal come bustion engine having a combustionspace, a

kspark plug formed outside of said space with,

a combustion chamber having a restricted opening communicating with saidspace, and a pair of spark gaps arranged in series and disposed one oneach side of said restricted opening, substantially as described.

29. A spark plug for internal combustion engines comprising a bodyformed with a restricted chamber adapted to communicate with thecombustion space thereof, a grounded terminal carried thereby, anelectrode insulated from and extending through said body into saidchamber, and a neutral electrode insulated from said body and interposedbetween said grounded terminal and said electrode.

.30. `A spark plug for internal combustion engines comprising a. bodyformed with a restricted chamber adapted to communicate with thecombustion space thereof, a grounded terminal carried thereby, anelectrode insulated from and extending through said-body into saidchamber, and a neutral electrode mounted within said chamber ad-'jaceiit said electrode extending through said restricted chamberadjacent said grounded terminal.

3l. A spark plug for internal combustion engines comprising a bodyformed with a restricted chamber adapted to communicate with thecombustion space thereof, and electrodes arranged in series andinsulated from said body providing a plurality of spark gaps. L

32. A spark plug for internal combustion engines comprising a bodyformed with a combustion chamber adapted to communicate with thecombustion space thereof and electrodes mounted in said combustionchainber and arranged in series providing a plurality of spark gaps. i

33. A spark plug, adapted to have one end inserted in the wall of thecylinder of an internal combustion engine, having an insulator with achamber, Within the plug, having coniii'innication with the enginecylinder;

` electrodes forming a spark gap in said chainbei'` one of saidelectrodes being hollow and having an opening into said chamber wherebygases may pass through the electrode to and from said Chamber.

34. A spank plug having a Vbody portion dapted for insertion in the wallof the cylinder ot an internal combustion engine, and having spark gapelectrodes; a chamber within said plug, beyond ysaid body portion andoutside of said cylinder having communication withthe cylinder; andother spark (Isp electrodes, within said chamber, in series with thefirst` mentioned electrodes.

35. A spark plug having a body portion adapted for insertion in the wallof the cylinder of an internal combustion engine, and having conductorsarranged to form two spark gaps in series lengthwise of the plus, bothgaps being set in spaces accessible to explosive mixture ol the enginecylinder; one ofsaid s )aces being outside of the engine cylinder anbeyond said body portion.

`36. A.V spark plug having, in con'ibinatiom an inner conducting jacketadapted for inseition in the wall ot' the cylinder lof an internalcombustion engine and having a spark gap terminal; an outer casingadapted to be positioned outside of the cylinder and having a chamber;aii insulating element extending into the jacket and disposed betweenthe acket and the outer casing and having a passage communicating with'the chamber and with the cylinder for transfer of gases between thechamber and the cylinder; an electrode cariied by the outer casinghaving a `.spark gap terminal in the chamber; a second electrode,insulated fromy the first mentioned electrode and mounted in theinsulating element and having a spark gap terminal cooperating with thefirst mentioned terminal to form a spark gap in the chamber; the secondelectrode being insulated bythe insulating element from the jacket, andhaving a second spark gap terminal cooperating with the jacket terminalto form a spark gap in the cylinder; whereby the said spark gaps aredisposed in series.

Signed at Boston, Massachusetts, this twentieth day of February, 1922.

WILLIAM L. PHILLIPS.

